EP2316860B1 - Nitrile rubbers - Google Patents

Abstract

Producing nitrile rubbers, comprises carrying out emulsion polymerization of at least one alpha ,beta -unsaturated nitrile, at least one conjugated diene and optionally at least one further copolymerizable monomer. The emulsion polymerization is carried out using a redox system, which comprises (a) at least one peroxo compound as an oxidizing agent, (b) at least a reducing agent and (c) iron(II)chloride. Independent claims are also included for: (1) the nitrile rubber comprising repeating units, obtained by the above mentioned method or obtained from the nitrile rubber by subjecting to a metathesis reaction; (2) a hydrogenated nitrile rubber obtained from the nitrile rubber, by subjecting them to a hydrogenation reaction or by subjecting them to a metathesis reaction and subsequent hydrogenation; (3) a vulcanizable mixture comprising the nitrile rubber or hydrogenated nitrile rubber and at least one crosslinking agent; (4) producing a vulcanizate, comprising subjecting the vulcanizable mixture to crosslinking, preferably by increasing the temperature or photo-chemical activation; and (5) the vulcanizate obtained by the above mentioned method.

Description

The invention relates to a process for the preparation of novel, optionally hydrogenated nitrile rubbers, these optionally hydrogenated nitrile rubbers as such and vulcanizable mixtures containing them, and also to a process for the preparation of vulcanizates from these mixtures and the vulcanizates obtained thereby.

Nitrile rubbers, also abbreviated to "NBR", are understood to mean rubbers which are copolymers or terpolymers of at least one α, β-unsaturated nitrile, at least one conjugated diene and optionally one or more further copolymerizable monomers. Hydrogenated nitrile rubber, also abbreviated as "HNBR", is produced by hydrogenation of nitrile rubber. Accordingly, the C =C double bonds of the copolymerized diene units are completely or partially hydrogenated in HNBR. The degree of hydrogenation of the copolymerized diene units is usually in a range of 50 to 100%.

Processes for the preparation of such nitrile rubbers are known, see eg Ullmann's Encyclopedia of Industrial Chemistry, VCH Verlagsgesellschaft, Weinheim, 1993, pp. 255-261 , The polymerization to the nitrile rubbers is usually carried out as emulsion polymerization and can be started radically by azo initiators, persulfates, organic peroxides or redox systems. In the above. Reference Redox systems are described as predominantly used initiator systems, for example in the form of mixtures of organic peroxides, hydroperoxides or persulfates as oxidizing agents with reducing agents such as sodium dithionite or Rongalit (sodium formaldehyde sulfoxylate). Metal salts are optionally used as a cocatalyst, preferably with the addition of suitable complexing agents such as sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, isophthalic acid, trisodium phosphate or tetrapotassium diphosphate. Whether and, if appropriate, what influence the initiator system has on the properties of the rubber has not been investigated and is ignored.

In EP-A-0 692 496 . EP-A-0 779 301 and EP-A-0 779 300 The Zeon Corporation describes nitrile rubbers based on an unsaturated nitrile and a conjugated diene. Common to all nitrile rubbers is that they contain 10-60% by weight of unsaturated nitrile and have a Mooney viscosity in the range of 15-150, or respectively EP-A-0 692 496 of 15-65 and all having at least 0.03 moles of a specific C ₁₂ -C ₁₆ alkylthio group per 100 moles of monomeric units. The preparation of the nitrile rubbers is carried out in the presence of a correspondingly constructed C ₁₂ -C ₁₆ -alkylthiol as a molecular weight regulator, which acts as a "chain transfer agent" and is thus incorporated as an end group in the polymer chains. In the described patent applications, the polymerization is characterized by unspecified organic peroxides, Redox initiators, azo compounds or persulfates started. Any influence of the initiator system on the properties of the rubber is not considered.

In US-A-2,451,180 The Goodrich Company discloses the polymerization to produce poly-1,3-butadienes and copolymers of 1,3-butadiene with other copolymerizable monomers such as acrylonitrile using small amounts of Group VIII water-soluble metal salts of the Mendeleyev Periodic Table based on iron, cobalt , Nickel, palladium, osmium, platinum, etc. described. Iron, cobalt and nickel salts are mentioned as preferred salts. As typical examples of such salts, chlorides, nitrates, iodides, bromides, sulfates, sulfites, nitrites, thiocyanates of iron, cobalt, nickel and other Group VIII metals are generally enumerated as long as they are water-soluble. With regard to metals that can occur in more than one oxidation state, it is generally stated that these could be used in both the oxidized and the reduced form, for example as iron (II) sulfate or iron (III) sulfate. It is stated that when these metal salts are used, regardless of whether other common initiators and accelerators are present or not, a considerable increase in the rate of polymerization is observed within a few hours and can be further polymerized at a low temperature of 20 to 30 ° C, resulting in polymers with improved properties, in particular improved Elongation at break and Tensile Strength. In the examples, NBR is polymerized in the presence of iron ammonium sulfate, cobalt chloride or nickel sulfate and using hydrogen peroxide. However, investigations into the properties of NBR vulcanizates are not found.

In US-A-2,897,167 The Dow Chemical Company describes the emulsion polymerization of conjugated diolefins with methyl isopropenyl ketone or with a mixture of methyl isopropenyl ketone and another vinylidene monomer (eg acrylonitrile) to give rubbers or stable latexes. It is particularly emphasized here that the use of the methyl isopropenyl ketone monomer is required in order to prevent the gel formation and thus the attack of pre-coagulated polymer in the latex produced. The polymerization is carried out in the presence of a redox system. The reducing agent used is sodium formaldehyde sulfoxylate, and the oxidizing agent is diisopropylbenzene hydroperoxide. In addition, redox-active iron in the form of iron (III) chloride or iron (II) sulfate is added. An influence of the iron-based redox initiator system on the properties of the produced rubber or latex is not disclosed.

In US-A-2,968,645 The company Dow Chemical Company describes the emulsion polymerization of rubbers in the presence of α- or β-conidendrol (naphtho (2,3-c) furan-1 (3H) -one). The α- or β-conidendrol is added to the polymerization, on the one hand the To increase the rate of polymerization and on the other hand to obtain its effect as an antioxidant after the polymerization. The monomers used are the isomers of butadiene and / or monoolefinic substances. For the redox system of this emulsion polymerization, according to the examples and the description, iron (III) chloride and iron (II) sulfate are added as metal salts. The influence which the components of the redox system may have on the properties of the rubber is not investigated.

Also from US-A-2,716,107 is the use of redox systems containing iron (III) chloride or iron (II) sulfate for the polymerization of 1,3-butadiene and one or more vinylic monomers, such as acrylonitrile known.

Both NBR and HNBR have been firmly established in the field of specialty elastomers for many years. They have an excellent property profile in terms of excellent oil resistance, good heat resistance, excellent resistance to ozone and chemicals, the latter in the case of HNBR even more pronounced than the NBR. They also have very good mechanical and performance properties. For this reason, they are widely used in a variety of applications and are used, for example, for the production of seals, hoses, belts and damping elements in the automotive sector, also for stators, borehole seals and valve seals in the field of oil production and also for many parts of the electrical industry, the machine industry. and shipbuilding. Commercially available are a variety of different types, which are characterized by different monomers, molecular weights, polydispersities and mechanical and physical properties depending on the application. In addition to the standard types, especially special grades with contents of special termonomers or special functionalizations are increasingly in demand. There is still a need for types which have good and easy processability, in particular very good flowability, and whose vulcanizates show a good mechanical property profile. For example, grades with improved flowability can hitherto be prepared by using an additional metathesis process step, whereby a significantly lower Mooney viscosity and thus a lower average molecular weight can be set in the nitrile rubbers. Since this is an additional process step, this is not unreservedly positive in economic terms, and the nitrile rubber types obtained do not meet all the requirements with regard to the property profile.

The object of the present invention was therefore to provide a process which enables the synthesis of nitrile rubbers which have good and easy processability, in particular flowability, and whose vulcanizates show a very good mechanical property profile. This object is achieved by a new process for the preparation of nitrile rubbers, in which a special redox system is used as an initiator for the emulsion polymerization.

1. (i) als Oxidationsmittel mindestens eine Peroxoverbindung,
2. (ii) mindestens ein Reduktionsmittel und
3. (iii) Fe-II-Chlorid

enthält. The invention therefore provides a process for the preparation of nitrile rubbers by emulsion polymerization of at least one α, β-unsaturated nitrile, at least one conjugated diene and optionally one or more further copolymerizable monomers, characterized in that the emulsion polymerization is carried out using a redox system, which

1. (i) as oxidizing agent at least one peroxo compound,
2. (ii) at least one reducing agent and
3. (iii) Fe (II) chloride

contains.

The process according to the invention can also be used for the preparation of hydrogenated nitrile rubbers by subsequently carrying out a hydrogenation reaction. This hydrogenation reaction may also be preceded by a metathesis reaction for molecular weight reduction.

1. (i) als Oxidationsmittel mindestens eine Peroxoverbindung,
2. (ii) mindestens ein Reduktionsmittel und
3. (iii) Fe-II-Chlorid

und eine im Fall der hydrierten Nitrilkautschuke sich anschließende Hydrierung. The invention further provides optionally hydrogenated nitrile rubbers having repeating units derived from at least one α, β-unsaturated nitrile, at least one conjugated diene and optionally one or more other copolymerizable monomers obtainable by emulsion polymerization of at least one unsaturated nitrile, at least one conjugated diene and optionally one or more other copolymerizable monomers using a redox system containing

1. (i) as oxidizing agent at least one peroxo compound,
2. (ii) at least one reducing agent and
3. (iii) Fe (II) chloride

and a subsequent hydrogenation in the case of the hydrogenated nitrile rubbers.

Surprisingly, it is possible to provide by the process according to the invention on procedurally simple way, the special new nitrile rubbers and fully or partially hydrogenated new nitrile rubbers. These new rubbers are unexpectedly distinguished from the known nitrile rubbers by a very low long chain branching and a very low gel content. They therefore have a high flowability and can therefore be processed very easily. The optionally hydrogenated nitrile rubbers also have a significantly more uniform distribution of the various monomers along the polymer chains than nitrile rubbers obtained using other redox systems. This unexpected effect can, as described below, across the width of the glass transition temperature (derived from the Gordon Taylor relationship). In this way, the fundamental problem is solved for the first time that the conjugated dienes used for the preparation of nitrile rubbers, in particular 1,3-butadiene, and α, β-unsaturated nitriles, in particular acrylonitrile, have a very different reactivity and hitherto only by a corresponding metering regime In the course of the polymerization, it was possible to ensure that the amount of product produced contains polymer molecules having a sufficient chemical uniformity, that is to say a uniform distribution of the various monomers along the polymer chains.

In addition, vulcanizates, which are produced from the optionally hydrogenated nitrile rubbers, have an unchanged very good property profile.

In the aforementioned publications of the prior art, there is no disclosure or indication as to whether and, if appropriate, in what form a radical emulsion polymerization can influence the properties of the nitrile rubbers by choice or composition of specific redox initiator systems. In particular, the influence of the chloride over the sulfate as an anion was completely surprising, since in the literature in the experimental examples again and again only iron (II) sulfates were used (see US-A-2,897,167 and US-A-2,716,107 ).

NBR:

The nitrile rubbers according to the invention have repeating units of at least one α, β-unsaturated nitrile, at least one conjugated diene and optionally one or more further copolymerizable monomers.

The conjugated diene can be of any nature. Preference is given to using (C ₄ -C ₆ ) -conjugated dienes. Particular preference is given to 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, 1,2-butadiene, piperylene, 1,3-pentadiene or mixtures thereof. Particular preference is given to 1,3-butadiene and isoprene or mixtures thereof. Very particular preference is given to 1,3-butadiene.

As α, β-unsaturated nitrile, any known α, β-unsaturated nitrile can be used, preferred are (C ₃ -C ₅ ) -α, β-unsaturated nitriles such as acrylonitrile, methacrylonitrile, 1-chloroacrylonitrile, ethacrylonitrile, 2-cyanoacrylates or Mixtures thereof. Particularly preferred is acrylonitrile.

A particularly preferred nitrile rubber is a copolymer of acrylonitrile and 1,3-butadiene.

The optionally hydrogenated nitrile rubber of the present invention may be derived besides those derived from at least one conjugated diene and at least one α, β-unsaturated nitrile Repeating units also contain repeating units derived from one or more other copolymerizable monomers.

For example, carboxyl-containing, copolymerizable termonomers, preferably α, β-unsaturated monocarboxylic acids, their esters or amides, α, β-unsaturated dicarboxylic acids, their mono- or diesters and the corresponding anhydrides or amides, are suitable for this purpose.

Acrylic acid and methacrylic acid may preferably be used as α, β-unsaturated monocarboxylic acids .

It is also possible to use esters of α, β-unsaturated monocarboxylic acids , preferably their alkyl esters and alkoxyalkyl esters. Preference is given to the alkyl esters, in particular C ₁ -C ₁₈ alkyl esters of α, β-unsaturated monocarboxylic acids. Particular preference is given to alkyl esters, in particular C ₁ -C ₁₈ -alkyl esters of acrylic acid and of methacrylic acid, in particular methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth ) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, n-dodecyl (meth) acrylate and lauryl (meth) acrylate. In particular, n-butyl acrylate is used. Also preferred are alkoxyalkyl esters of α, β-unsaturated monocarboxylic acids, particularly preferably alkoxyalkyl esters of acrylic acid or of methacrylic acid, in particular C ₂ -C ₁₂ -alkoxyalkyl esters of acrylic acid or of methacrylic acid, very particularly preferably methoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate and methoxyethyl (meth) acrylate. In particular, methoxyethyl acrylate is used. It is also possible to use mixtures of alkyl esters, such as those mentioned above, with alkoxyalkyl esters, for example in the form of the abovementioned. It is also possible to use cyanoalkyl acrylates and cyanoalkyl methacrylates in which the C atom number of the cyanoalkyl group is 2-12, preferably α-cyanoethyl acrylate, β-cyanoethyl acrylate and cyanobutyl methacrylate. It is also possible to use hydroxyalkyl acrylates and hydroxyalkyl methacrylates in which the C atom number of the hydroxyalkyl groups is 1-12, preferably hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and hydroxybutyl (meth) acrylate. It is also possible to use fluorine-substituted benzyl-containing acrylates or methacrylates, preferably fluorobenzyl (meth) acrylate. It is also possible to use fluoroalkyl group-containing (meth) acrylates, preferably trifluoroethyl acrylate and tetrafluoropropyl methacrylate. It is also possible to use amino-containing αβ-unsaturated carboxylic acid esters, such as dimethylaminomethyl acrylate and diethylaminoethyl acrylate.

Other esters of the α, β-unsaturated monocarboxylic acids are, for example, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, glycidyl (meth) acrylate, Epoxy (meth) acrylate, N- (2-hydroxyethyl) acrylamides, N- (2-hydroxymethyl) acrylamides and urethane (meth) acrylate used.

Further copolymerizable monomers which can also be used are α, β-unsaturated dicarboxylic acids , preferably maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid and mesaconic acid.

It is also possible to use α, β-unsaturated dicarboxylic acid anhydrides , preferably maleic anhydride, itaconic anhydride, citraconic anhydride and mesaconic anhydride.

Can also be used mono- or diesters of α, β-unsaturated dicarboxylic acids . These are, for example, alkyl, preferably C ₁ -C ₁₀ -alkyl, in particular ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl or n-hexyl, alkoxyalkyl -, Preferably C ₂ -C ₁₂ alkoxyalkyl, particularly preferably C ₃ -C ₈ alkoxyalkyl, hydroxyalkyl, preferably C ₁ -C ₁₂ hydroxyalkyl, particularly preferably C ₂ -C ₈ - hydroxyalkyl, cycloalkyl, preferably C ₅ -C _12- cycloalkyl, particularly preferably C ₆ -C ₁₂ -cycloalkyl, alkylcycloalkyl, preferably C ₆ -C ₁₂ -alkylcycloalkyl, particularly preferably C ₇ -C ₁₀ -alkylcycloalkyl, aryl, preferably C ₆ -C ₁₄ -aryl Mono- or diesters, which may also be mixed esters in the case of diesters.

Examples of α, β-unsaturated dicarboxylic acid monoesters include

• Maleic monoalkyl esters, preferably monomethyl maleate, monoethyl maleate, monopropyl maleate and mono-n-butyl maleate;
• Maleic monocycloalkyl esters, preferably monocyclopentyl maleate, monocyclohexyl maleate and monocycloheptyl maleate;
• Maleic acid monoalkylcycloalkyl ester, preferably monomethylcyclopentyl maleate and monoethylcyclohexyl maleate;
• Maleic monoarylester, preferably monophenylmaleate;
• Maleic acid monobenzyl ester, preferably monobenzyl maleate;
• Fumaric acid monoalkyl esters, preferably monomethyl fumarate, monoethyl fumarate, monopropyl fumarate and mono-n-butyl fumarate;
• Fumaric monocycloalkyl esters, preferably monocyclopentyl fumarate, monocyclohexyl fumarate and monocycloheptyl fumarate;
• Fumaric acid monoalkylcycloalkyl ester, preferably monomethylcyclopentyl fumarate and monoethylcyclohexyl fumarate; Fumaric monoaryl ester, preferably monophenyl fumarate;
• Fumaric acid monobenzyl ester, preferably monobenzyl fumarate;
• Citraconic monoalkyl esters, preferably monomethyl citraconate, monoethyl citraconate, monopropyl citraconate and mono-n-butyl citraconate;
• Citraconic monocycloalkyl esters, preferably monocyclopentyl citrate, monocyclohexyl citrate and monocycloheptyl citrate;
• Citraconsäuremonoalkylcycloalkylester, preferably Monomethylcyclopentylcitraconat and Monoethylcyclohexylcitraconat;
• Citraconsäuremonoarylester, preferably Monophenylcitraconat;
• Citraconic acid monobenzyl ester, preferably monobenzyl citraconate;
• Itaconic acid monoalkyl ester, preferably monomethyl itaconate, monoethyl itaconate, monopropyl itaconate and mono-n-butyl itaconate;
• Itaconic acid monocycloalkyl ester, preferably monocyclopentyl itaconate, monocyclohexyl itaconate and monocycloheptyl itaconate;
• Itaconic acid monoalkylcycloalkyl ester, preferably monomethylcyclopentyl itaconate and monoethylcyclohexyl itaconate;
• Itaconic acid monoaryl ester, preferably monophenyl itaconate;
• Itaconic acid monobenzyl ester, preferably monobenzyl itaconate.
• Mesaconsäuremonoalkylester, preferably Mesaconsäuremonoethylester;

As α, β-unsaturated dicarboxylic acid diesters, the analog diesters can be used based on the aforementioned monoester groups, wherein the ester groups may also be chemically different.

Further possible monomers are vinylaromatics such as styrene, α-methylstyrene and vinylpyridine, as well as non-conjugated dienes such as 4-cyanocyclohexene (4-CCN) and 4-vinylcyclohexene (VCH), and alkynes, in particular 1- or 2-butyne.

It is also possible to use as further copolymerizable monomers radically polymerizable compounds containing per molecule two or more olefinic double bonds. Examples of such polyunsaturated or polyunsaturated compounds are di- or polyunsaturated acrylates, methacrylates or itaconates of polyols such as 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate (EGDMA), diethylene glycol dimethacrylate, triethylene glycol diacrylate, 1,4-butanediol diacrylate, propanediol-1,2-diacrylate, butanediol-1,3-dimethacrylate, neopentyl glycol diacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolethane diacrylate, trimethylolethane dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate (TMPTMA), glycerol di- and triacrylate, pentaerythritol di-, tri- and tetra-acrylate or methacrylate, dipentaerythritol tetra, penta- and - hexaacrylate or methacrylate or itaconate, sorbitol tetraacrylate, sorbitol hexamethacrylate, diacrylates or dimethacrylates of 1,4-cyclohexanediol, 1,4-dimethylolcyclohexane, 2,2-bis (4-hydroxyphenyl) propane, of polyethylene glycols or of oligoesters or oligourethanes with hydroxyl end groups , As polyunsaturated monomers it is also possible to use acrylamides such as, for example, methylenebisacrylamide, hexamethylene-1,6-bisacrylamide, diethylenetriamine-tris-methacrylamide, bis (methacrylamido-propoxy) ethane or 2-acrylamidoethyl acrylate. Examples of polyunsaturated vinyl and allyl compounds are divinylbenzene, ethylene glycol divinyl ether, diallyl phthalate, allyl methacrylate, diallyl maleate, triallyl isocyanurate or triallyl phosphate.

The proportions of conjugated diene and α, β-unsaturated nitrile in the optionally hydrogenated nitrile rubbers according to the invention can vary within wide ranges. The proportion of or the sum of the conjugated dienes is usually in the range of 20 to 95 wt.%, Preferably in the range of 40 to 90 wt .-%, particularly preferably in the range of 50 to 85 wt.%, Based on the total polymer. The proportion of or the sum of the α, β-unsaturated nitriles is usually from 5 to 80% by weight, preferably from 10 to 60% by weight, more preferably from 15 to 50% by weight, based on the total polymer. The proportions of the monomers in each case add up to 100% by weight.

The additional monomers can be present in amounts of from 0 to 40% by weight, preferably from 0.1 to 40% by weight, particularly preferably from 1 to 30% by weight, based on the total polymer. In this case, corresponding proportions of the conjugated dienes and / or of the α, β-unsaturated nitriles are replaced by the proportions of these additional monomers, wherein the proportions of all monomers continue to add up to 100 wt .-%. In the case of the presence of one or more termonomers, it has been found that the proportion of or the sum of the conjugated dienes is in the range from 40 to 90% by weight, preferably in the range from 50 to 85% by weight, based on the Total polymer, the proportion of or the sum of the α, β-unsaturated nitriles at 9.9 to 59.9 wt .-%, preferably 14 to 50 wt .-%, based on the total polymer, and the proportions of or Sum of the termonomers in the range of 0.1 to 30 wt .-%, preferably 1 to 20 wt .-%, based on the total polymer, wherein the proportions of all monomers must add up to 100 wt.% Each.

If esters of (meth) acrylic acid are used as additional termonomers, this usually takes place in amounts of from 1 to 25% by weight, based on the total polymer

If α, β-unsaturated mono- or dicarboxylic acids are used as additional termonomers, this is usually carried out in amounts of less than 10% by weight, based on the total polymer. The nitrogen content for determining the acrylonitrile content is determined in the nitrile rubbers according to the invention in accordance with DIN 53 625 according to Kjeldahl. Due to the content of polar comonomers, the nitrile rubbers are usually soluble in methyl ethyl ketone at 20 ° C ≥ 85 wt.%.

Preference is given to nitrile rubbers according to the invention which have repeating units of acrylonitrile, 1,3-butadiene and optionally one or more further copolymerisable monomers. Also preferred are nitrile rubbers, the repeat units of acrylonitrile, 1,3-butadiene and one or more α, β-unsaturated mono- or dicarboxylic acids, their esters or amides, in particular repeat units of an alkyl ester of an α, β-unsaturated carboxylic acid, most preferably of methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate or lauryl (meth) acrylate.

The nitrile rubbers according to the invention, which may also be wholly or partly hydrogenated, have Mooney viscosities (ML (1 + 4 @ 100 ° C.)) of from 10 to 160, preferably from 15 to 150 Mooney units, particularly preferably from 20 to 150 Mooney. Units and in particular 25 to 145 Mooney units on. The values for the Mooney viscosity (ML 1 + 4 at 100 ° C.) are determined in each case by means of a shear disk viscometer in accordance with DIN 53523/3 or ASTM D 1646 at 100 ° C.

The nitrile rubbers used furthermore have a polydispersity PDI = M _w / M _n , where M _{w is} the weight average and M _n the number average molecular weight, in the range from 2.0 to 6.0, and preferably in the range from 2.0 to 5, 0th

The glass transition temperatures of the nitrile rubbers according to the invention, which may also be completely or partially hydrogenated, are in the range from -70.degree. C. to + 10.degree. C., preferably in the range from -60.degree. C. to 0.degree. The determination of the glass transition temperature, and their so-called onset and offset points by means of differential scanning calorimetry ( DSC) according to ASTM E 1356-03 and DIN 11357-2.

jeweils für den Onset- bzw. Offsetpunkt ein ACN-Gehalt ([ACN]) berechnet werden, und aus diesen ein Differenzwert (ΔACN) der ACN-Verteilung gebildet werden: $$\mathrm{\Delta ACN}=\mathrm{ACN}\left(\mathrm{Offset}\right)-\mathrm{ACN}\left(\mathrm{Onset}\right)$$

Based on the measured onset and offset points can be determined by the Gordon-Taylor relationship $$T_G=1.4564*\left[\mathit{ACN}\right]-77.147$$

An ACN content ([ACN]) is calculated in each case for the onset or offset point, and from these a difference value (ΔACN) of the ACN distribution is formed: $$\mathrm{\Delta ACN}=\mathrm{ACN}\left(\mathrm{offset}\right)-\mathrm{ACN}\left(\mathrm{Onset}\right)$$

This difference ΔACN represents a measure of unity.

The course of vulcanization on the MDR and its analytical data are measured on a Monsanto rheometer MDR 2000 according to ASTM D5289-95.

The determination of the MSR (Mooney Stress Relaxation) is carried out in each case by means of a shear disk viscometer according to ISO 289-4: 2003 (E) at 100 ° C.

Preparation of the Nitrile Rubbers According to the Invention:

The preparation of the nitrile rubbers takes place by emulsion polymerization. Of essential importance is the redox system used. This contains to initiate the emulsion polymerization an oxidizing agent (i), which decomposes into free radicals.

The oxidizing agents (i) used are peroxo compounds, ie compounds which have an -OU unit. The peroxo compounds include hydrogen peroxide, peroxodisulfates, peroxodiphosphates, hydroperoxides, peracids, peracid esters, peracid anhydrides and peroxides having two organic radicals. As salts of peroxodisulfuric acid and peroxodiphosphoric acid, sodium, potassium and ammonium salts can be used. Suitable hydroperoxides include t-butyl hydroperoxide, cumene hydroperoxide and p-menthane hydroperoxide. Suitable peroxides having two organic radicals are dibenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, di-t-butyl peroxide, dicumyl peroxide, t-butyl perbenzoate and t-butyl peracetate.

Preference is given to using p-menthane hydroperoxide or pinane hydroperoxide.

Examples of suitable reducing agents (ii) are sodium formaldehyde sulfoxylate, sodium benzaldehydesulfoxylate, reducing sugars, ascorbic acid, sulfenates, sulfinates, sulfoxylates, dithionite, sulfite, metabisulfite, disulfite, sugars, urea, thiourea, xanthates, thioxanthogenates, hydrazinium salts, amines and amine derivatives such as aniline, dimethylaniline, Monoethanolamine, diethanolamine or triethanolamine are used, preferred is sodium formaldehyde sulfoxylate.

The amount of oxidizing agent (i) is usually 0.001 to 1 part by weight based on 100 parts by weight of monomers. The molar amount of reducing agent (ii) is in the range of 1 to 1000 mol% based on the molar amount of the oxidizing agent (i) used. Preferably, the molar amount of reducing agent (ii) is in the range of 2 to 100% based on the molar amount of the oxidizing agent (i) used.

The iron (II) chloride used is preferably FeCl ₂ .4H ₂ O.

Other possible additives which can be added in the process according to the invention are complexing agents and salts, e.g. Trisodium phosphate. As complexing agents are e.g. Sodium ethylenediaminetetraacetate (EDTA), sodium silicate, sodium pyrophosphate or sodium polyphosphate, of which EDTA is preferred. The molar amount of complexing agent refers to the amount of iron (II) chloride used, and is usually chosen at least equimolar with this.

In a preferred embodiment, the inventive method is carried out using a redox system containing as peroxide p-menthane hydroperoxide or pinane hydroperoxide, as a reducing agent sodium formaldehyde sulfoxylate and Fe-II chloride (FeCl ₂ * 4 H ₂ O). In a particularly preferred embodiment, the process of the invention is carried out using this particular redox system and in the additional presence of sodium ethylenediaminetetraacetate.

To carry out the polymerization, individual, several or all components of the redox system are metered in at the beginning of the polymerization or during the polymerization. If the metered addition at the beginning of the polymerization, the components of the redox system are added either together or individually in the submitted reaction mixture containing water, the monomers and the emulsifier. It has been found useful to add the reducing agent and the Fe (II) chloride in the form of a premix solution while adding the oxidizing agent separately.

As emulsifiers water-soluble salts of anionic emulsifiers or neutral emulsifiers can be used. Anionic emulsifiers are preferably used.

Modified resin acids obtained by dimerization, disproportionation, hydrogenation and modification of resin acid mixtures containing abietic acid, neoabietic acid, palustric acid, levopimaric acid can be used as anionic emulsifiers. A particularly preferred modified rosin acid is the disproportionated rosin acid ( Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Volume 31, pp. 345-355 ).

As anionic emulsifiers and fatty acids can be used. These contain 6 to 22 C atoms per molecule. They can be fully saturated or contain one or more double bonds in the molecule. Examples of fatty acids are caproic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid. The carboxylic acids are usually based on origin-specific oils or fats such. Castoroil, cottonseed, peanut oil, linseed oil, coconut fat, palm kernel oil, olive oil, rapeseed oil, soybean oil, fish oil and beef tallow, etc. ( Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Vol. 13, pp. 75-108 ). Preferred carboxylic acids are derived from coconut fatty acid and beef tallow and are partially or completely hydrogenated.

Such carboxylic acids based on modified resin acids or fatty acids are used as water-soluble lithium, sodium, potassium and ammonium salts. Na and K salts are preferred.

Anionic emulsifiers are also sulfonates, sulfates and phosphates bonded to an organic radical. Suitable organic radicals are aliphatic, aromatic, alkylated aromatics, fused aromatics, and methylene-bridged aromatics, where the methylene-bridged and fused aromatics may additionally be alkylated. The length of the alkyl chains is 6 to 25 C atoms. The length of the alkyl chains bonded to the aromatics is between 3 and 12 C atoms.

The sulfates, sulfonates and phosphates are used as lithium, sodium, potassium or ammonium salts. The sodium, potassium and ammonium salts are preferred.

Examples of such sulfonates, sulfates and phosphates are Na lauryl sulfate, Na alkyl sulfonate, Na alkylarylsulfonate, Na salts methylenverbrückter arylsulfonates, Na salts of alkylated naphthalenesulfonates and Na salts of methyleneverbrückter Napthalinsulfonate, which may also be oligomerized, the degree of oligimerization between 2 to 10 lies. Usually, the alkylated naphthalenesulfonic acids and the methylene-bridged (and optionally alkylated) naphthalenesulfonic acids are present as mixtures of isomers, which may also contain more than 1 sulfonic acid group (2 to 3 sulfonic acid groups) in the molecule. Particular preference is given to Na lauryl sulfate, Na alkylsulfonate mixtures having 12 to 18 C atoms, Na alkylaryl sulfonates, Na diisobutylene naphthalene sulfonate, methylene-bridged polynaphthalenesulfonate mixtures and methylene-bridged aryl sulfonate mixtures.

Neutral emulsifiers are derived from addition products of ethylene oxide and propylene oxide on compounds with sufficiently acidic hydrogen. These include, for example, phenol, alkylated phenol and alkylated amines. The average degrees of polymerization of the epoxides are between 2 and 20. Examples of neutral emulsifiers are ethoxylated nonylphenols having 8, 10 and 12 ethylene oxide units. The neutral emulsifiers are usually not used alone, but in combination with anionic emulsifiers.

Preference is given to the Na and K salts of disproportionated abietic acid and partially hydrogenated tallow fatty acid, and mixtures thereof, sodium lauryl sulfate, Na alkyl sulfonates, sodium alkyl benzene sulfonate and alkylated and methylene-bridged naphthalenesulfonic acids.

The emulsifiers are used in an amount of 0.2 to 15 parts by weight, preferably 0.5 to 12.5 parts by weight, particularly preferably 1.0 to 10 parts by weight, based on 100 parts by weight of the monomer mixture used.

If, after completion of the polymerization, latices are obtained which tend to premature self-coagulation due to a certain instability, the said emulsifiers can also be used for the post-stabilization of the latexes. This can be useful, in particular, before the removal of unreacted monomers by treatment with water vapor and before latex storage.

The emulsion polymerization can be carried out in the presence of molecular weight regulators. For example, find C ₁₂ mercaptans (eg in the form of tertiary dodecylmercaptans, also referred to in the literature as "TDDM") either individually or as a mixture or C ₁₆ mercaptans either individually or as a mixture application. Such molecular weight regulators are commercially available, for example from Phillips. The use of a mixture of C ₁₂ -mercaptans from 2,2,4,6,6-pentamethylheptanethiol-4, 2,4,4,6,6-pentamethylheptanethiol-2,2,3,4,6,6 has proven useful Pentamethylheptanethiol-2 and 2,3,4,6,6-pentamethylheptanethiol-3. It can be used in amounts of from 0.05 to 3 parts by weight, preferably from 0.1 to 1.5 parts by weight, based on 100 parts by weight of the monomer mixture. The metering of such mercaptan compounds or mixtures is carried out either at the beginning of the polymerization or in portions during the polymerization, wherein the portionwise addition of all and individual components of the regulator mixture during the polymerization is preferred. Will the above? nitrile rubber is 2,2,4,6,6-pentamethylheptane-4-thio, 2,4,4,6,6-pentamethylheptane-2-thio, 2,3,4,6, 6-Pentamethylheptan-2-thio and / or 2,3,4,6,6-pentamethylheptane-3-thio end groups.

The polymerization time is in the range of 4 hours to 15 hours and depends essentially on the acrylonitrile content of the monomer mixture and the polymerization temperature. The polymerization temperature is in the range of 0 to 30 ° C, preferably in the range of 5 to 25 ° C. When sales in the range of 50 to 95%, preferably in the range of 70 to 90%, the polymerization is usually stopped. For this purpose, a stopper is added to the reaction mixture. Suitable examples are dimethyldithiocarbamate, Na nitrite, mixtures of dimethyldithiocarbamate and Na nitrite, hydrazine and hydroxylamine, and salts derived therefrom such as hydrazinium sulfate and hydroxylammonium sulfate, diethylhydroxylamine, diisopropylhydroxylamine, hydrosoluble salts of hydroquinone, sodium dithionite, phenyl-α-naphthylamine and aromatic phenols such as tert Butyl catechol, or phenothiazine.

The amount of water used in the emulsion polymerization is in the range of 100 to 900 parts by weight, preferably in the range of 120 to 500 parts by weight, more preferably in the range of 150 to 400 parts by weight of water based on 100 parts by weight the monomer mixture.

In the emulsion polymerization, acids or bases can also be added to the aqueous phase for pH adjustment as well as for pH buffering and to reduce the viscosity during the polymerization. For this purpose, salts of monovalent metals in the form of KOH, NaOH, sodium sulfate, sodium carbonate, sodium bicarbonate, LiCl, NaCl and KCl are usually used. Preference is given to sodium and potassium hydroxide, sodium bicarbonate, lithium, sodium and potassium chloride. The amounts of these electrolytes are in the range 0 to 1 parts by weight, preferably 0 to 0.5 parts by weight based on 100 parts by weight of the monomer mixture.

The polymerization can be carried out either batchwise or continuously in a stirred tank cascade.

If you want to chemically produce very uniform products, acrylonitrile or butadiene are postdosed, if the composition is outside the azeotropic butadiene / acrylonitrile ratio. Preference is given to replenishing with NBR types having acrylonitrile contents of from 10 to 34 and with types containing from 40 to 50% by weight of acrylonitrile ( W. Hofmann, Rubber Chem. Technol. 36 (1963) 1 ) the case. The replenishment takes place - as in the DD 154 702 indicated - preferably computer-controlled on the basis of a computer program. However, this replenishment is not necessary since, as already described, the advantage of the process according to the invention is that polymers with high chemical uniformity are already being supplied by the special redox system.

To remove unreacted monomers and volatile components of the stopped latex is subjected to a steam distillation. In this case, temperatures in the range of 70 ° C to 150 ° C are used, wherein at temperatures <100 ° C, the pressure is reduced. Before the removal of the volatile constituents, a post-stabilization of the latex with emulsifier can take place. For this purpose, it is expedient to use the abovementioned emulsifiers in amounts of 0.1 to 2.5% by weight, preferably 0.5 to 2.0% by weight. % based on 100 parts by weight of nitrile rubber.

Before or during latex coagulation one or more anti-aging agents can be added to the latex. For this purpose, phenolic, aminic and other anti-aging agents are suitable.

Suitable phenolic aging inhibitors are alkylated phenols, styrenized phenol, sterically hindered phenols such as 2,6-di-tert-butylphenol, 2,6-di-tert-butyl p -cresol (BHT), 2,6-di-tert. -butyl-4-ethylphenol, ester-group-containing sterically hindered phenols, thioether-containing sterically hindered phenols, 2,2'-methylenebis (4-methyl-6- tert- butylphenol) (BPH) and sterically hindered thiobisphenols.

If a discoloration of the rubber is of no importance, also aminic aging inhibitor z. B. mixtures of diaryl-p-phenylenediamines (DTPD), octylated diphenylamine (ODPA), phenyl-α-naphthylamine (PAN), phenyl-β-naphthylamine (PBN), preferably those based on phenylenediamine used. Examples of phenylenediamines are N-isopropyl-N 'phenyl-p-phenylenediamine, N-1,3-dimethylbutyl N'-phenyl-p-phenylenediamine (6PPD), N-1,4-dimethylpentyl N' -phenyl- p-phenylenediamine (7PPD), N, N '-bis-1,4- (1,4-dimethylpentyl) - p-phenylenediamine (77PD), etc.

Other anti-aging agents include phosphites such as tris (nonylphenyl) phosphite, polymerized 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ), 2-mercaptobenzimidazole (MBI), methyl 2-mercaptobenzimidazole (MMBI), zinc methylmercaptobenzimidazole ( ZMMBI). The phosphites are generally used in combination with phenolic anti-aging agents. TMQ, MBI and MMBI are mainly used for NBR grades that are vulcanized peroxide.

For coagulation, the latex is adjusted to a pH known to the person skilled in the art by adding a base, preferably ammonia or sodium or potassium hydroxide, or an acid, preferably sulfuric acid or acetic acid.

In one embodiment of the method, the coagulation is carried out using at least one salt selected from the group consisting of aluminum, calcium, magnesium, sodium, potassium and lithium salts. As anions of these salts usually monovalent or divalent anions are used. Preference is given to halides, particularly preferably chloride, nitrate, sulfate, bicarbonate, carbonate, formate and acetate.

Suitable examples are sodium chloride, potassium chloride, calcium chloride, magnesium chloride, sodium nitrate, potassium nitrate, sodium sulfate, potassium sulfate, sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, aluminum sulfate, potassium aluminum sulfate (potassium alum), sodium aluminum sulfate (sodium alum), sodium acetate, calcium acetate and calcium formate.

If a water-soluble calcium salt is used for latex coagulation, calcium chloride is preferred.

The concentration of the solution of one or more salts selected from the group consisting of aluminum, calcium, magnesium, sodium, potassium and lithium salts is 3 to 30 wt.%. For the preparation of the salt solution, water containing Ca ions is preferably used.

The total amount of salts necessary for the latex coagulation selected from the group consisting of aluminum, calcium, magnesium, sodium, potassium and lithium salts is 0.5-200% by weight, preferably 0.8-80% by weight. %, particularly preferably 1-50% by weight of salt, based on 100 parts by weight of nitrile rubber.

In addition to at least one salt selected from the group defined above, precipitants may also be used in the coagulation. Suitable precipitation aids are, for example, water-soluble polymers. These are nonionic, anionic or cationic.

Examples of nonionic polymeric precipitation aids are modified cellulose such as hydroxyalkyl cellulose or methyl cellulose and adducts of ethylene oxide and propylene oxide on compounds with acidic hydrogen. Examples of compounds having acidic hydrogen are: fatty acid, sugars such as sorbitol, mono- and difatty acid glycerides, phenol, alkylated phenols, (alkyl) phenol / formaldehyde condensates, etc. The addition products of ethylene oxide and propylene oxide to these compounds can be random and block-like. Of these products, those in which solubility decreases with increasing temperature are preferred. Characteristic turbidity temperatures are in the range 0 to 100 ° C, in particular in the range of 20 to 70 ° C.

Examples of anionic polymeric precipitation aids are the homopolymers and copolymers of (meth) acrylic acid, maleic acid, maleic anhydride, etc. The sodium salt of polyacrylic acid is preferred.

Cationic polymeric precipitants are usually based on polyamines and on homo- and copolymers of (meth) acrylamide. Preference is given to polymethacxrylamides and polyamines, in particular based on epichlorohydrin and dimethylamine. The amounts of polymeric precipitation aids are 0.01 to 5 parts by weight, preferably 0.05 to 2.5 parts by weight per 100 parts by weight of nitrile rubber.

The use of other precipitation aids is conceivable. It should be noted, however, that it is possible without problems, the inventive method with the desired success in the absence of additional precipitation aids, and in particular in the absence of C ₁ -C ₄ alkylcelluloses, hydroxyalkylcelluloses, plant-derived proteinaceous materials or polysaccharides, such as Starch, or water-soluble polyamine compounds.

The latex used for coagulation has expediently a solids concentration in the range of 1% to 40%, preferably in the range of 5% to 35% and particularly preferably in the range of 15 to 30% by weight.

The latex coagulation is carried out in the temperature range of 10 to 100 ° C, preferably at a temperature of 20 to 90 ° C. The latex coagulation can be continuous or discontinuous, preferably continuous.

In an alternative embodiment, the latex conventionally separated from unreacted monomers may also be treated with acids in a pH range of ≤ 6, whereby the polymer precipitates. The treatment is preferably carried out at a pH ≦ 4, particularly preferably 2.

The precipitation of the polymer is carried out at temperatures of 20 to 110 ° C, preferably 50 to 98 ° C, more preferably at 65 to 85 ° C. For precipitation all mineral and organic acids can be used, which allow to adjust the selected pH ranges. Mineral acids are preferably used for pH adjustment.

For the precipitation, a precipitating agent or precipitation aid may additionally be added. For example, the alkali metal salts of inorganic acids known to those skilled in the art and mixtures thereof are used as additional precipitating agents. Suitable alkali metal salts are, in particular, the sodium and potassium salts of the following acids: hydrochloric acid, sulfuric acid, sulphurous acid, nitric acid, nitrous acid and phosphoric acid. The sodium and potassium salts of hydrochloric acid and sulfuric acid are preferred. Particularly preferred is sodium chloride and sodium sulfate. The precipitants are added in an amount of 0.05 to 10% by weight, preferably 0.5 to 8% by weight, more preferably 1 to 5% by weight, based on the solids content of the latex dispersion. The precipitation aids already mentioned above can also be used here ,

The polymer suspension thus obtained is adjusted to a pH of ≥ 11 by addition of an aqueous alkali hydroxide solution. Preferably, the pH ≥ 11.5 is set. As aqueous alkali hydroxide solutions, solutions of sodium hydroxide or potassium hydroxide, preferably sodium hydroxide in water with an alkali metal hydroxide content of 10 to 50% are used. The alkaline treatment of the coagulated polymer is preferably carried out at 60 to 100 ° C, preferably at 65 to 95 ° C. After the alkaline treatment, the polymer is separated from the suspension in the conventional manner. This variant of the latex coagulation can also be carried out continuously or discontinuously, preferably working continuously.

After coagulation, the nitrile rubber is usually present in the form of so-called crumbs. The laundry of the coagulated NBR is therefore also referred to as crumb laundry. For this wash either deionized water or non-deionized water can be used. The washing is carried out at a temperature in the range of 15 to 90 ° C, preferably at a temperature in the range of 20 to 80 ° C. The amount of washing water is 0.5 to 20 parts by weight, preferably 1 to 10 parts by weight, and more preferably 1 to 5 parts by weight, based on 100 parts by weight of nitrile rubber. Preferably, the rubber crumbs are subjected to a multi-stage washing, wherein the rubber crumbs are partially dewatered between the individual washing stages. The residual moistures of the crumbs between the individual washing stages are in the range from 5 to 50% by weight, preferably in the range from 7 to 25% by weight. The number of washing stages is usually from 1 to 7, preferably from 1 to 3. The washing is carried out batchwise or continuously. Preference is given to using a multistage, continuous process, with countercurrent washing being preferred for the careful handling of water. After completion of the wash, it has been proven to dehydrate the nitrile rubber crumbs.

The invention furthermore relates to vulcanizable mixtures comprising at least one nitrile rubber according to the invention, which may also be completely or partially hydrogenated, and at least one crosslinker. Optionally, one or more further additives are also included.

These vulcanizable mixtures are prepared by mixing at least one optionally hydrogenated nitrile rubber according to the invention and at least one crosslinker. Optionally, one or more further additives are further mixed.

Suitable crosslinkers are, for example, peroxidic crosslinkers such as bis (2,4-dichlorobenzyl) peroxide, dibenzoyl peroxide, bis (4-chlorobenzoyl) peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcylohexane, tert-butyl peroxide. Butyl perbenzoate, 2,2-bis (t-butylperoxy) butene, 4,4-di-tert-butyl peroxynonyl valerate, dicumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, tert-butyl cumyl peroxide, 1 , 3-bis (t-butylperoxyisopropyl) benzene, di-tert-butyl peroxide and 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyn-3.

It may be advantageous, in addition to these peroxidic crosslinkers, to use further additives with the aid of which the crosslinking yield can be increased. For example, triallyl isocyanurate, triallyl cyanurate, trimethylolpropane tri (meth) acrylate, triallyl trimellitate, ethylene glycol dimethacrylate, butanediol dimethacrylate, trimethylolpropane trimethacrylate, Zn-diacrylate, Zn dimethacrylate, 1,2-polybutadiene or N, N'-m-phenylenedimaleimide.

The total amount of crosslinker (s) is usually in the range of 1 to 20 phr, preferably in the range of 1.5 to 15 phr and more preferably in the range of 2 to 10 phr, based on the nitrile rubber.

As a crosslinker, sulfur in elemental soluble or insoluble form or sulfur donors can be used.

Suitable sulfur donors are, for example, dimorpholyl disulfide (DTDM), 2-morpholinodithiobenzothiazole (MBSS), caprolactam disulfide, dipentamethylene thiuram tetrasulfide (DPTT), and tetramethylthiuram disulfide (TMTD).

Even in the case of sulfur vulcanization of the nitrile rubbers according to the invention, it is possible to use further additives with the aid of which the crosslinking yield can be increased. In principle, however, the crosslinking can also take place with sulfur or sulfur donors alone.

Conversely, however, the crosslinking of the nitrile rubbers according to the invention can also be carried out only in the presence of the abovementioned additives, i. without the addition of elemental sulfur or sulfur donors.

As additives with the aid of which the crosslinking yield can be increased, e.g. Dithiocarbamates, thiurams, thiazoles, sulfenamides, xanthogenates, bi- or polycyclic amines, guanidine derivatives, dithiophosphates, caprolactams and thiourea derivatives.

As dithiocarbamates can be used, for example: ammonium dimethyldithiocarbamate, sodium diethyldithiocarbamate (SDEC), Natriumdibutyl-dithiocarbamate (SDBC), zinc dimethyldithiocarbamate (ZDMC), zinc diethyldithiocarbamate (ZDEC), zinc dibutyldithiocarbamate (ZDBC), zinc ethylphenyldithiocarbamate (ZEPC), zinc dibenzyldithiocarbamate (ZBEC), zinc pentamethylenedithiocarbamate (Z5MC) , Tellurium diethyldithiocarbamate, nickel dibutyldithiocarbamate, nickel dimethyldithiocarbamate and zinc diisononyl dithiocarbamate.

As thiurams, there may be used, for example, tetramethylthiuram disulfide (TMTD), tetramethylthiuram monosulfide (TMTM), dimethyldiphenylthiuram disulfide, tetrabenzylthiuram disulfide, dipentamethylenethiuram tetrasulfide and tetraethylthiuram disulfide (TETD).

As thiazoles, there may be used, for example, 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), zinc mercaptobenzothiazole (ZMBT) and copper 2-mercaptobenzothiazole.

Examples of sulfenamide derivatives which can be used are: N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), N-tert-butyl-2-benzthiazyl sulfenamide (TBBS), N, N'-dicyclohexyl-2-benzthiazyl sulfenamide (DCBS), 2-morpholinothiobenzothiazole ( MBS), N-oxydiethylenethiocarbamyl-N-tert-butylsulfenamide and oxydiethylenethiocarbamyl-N-oxyethylenesulfenamide.

As xanthates, there may be used, for example, sodium dibutylxanthogenate, zinc isopropyldibutylxanthogenate and zinc dibutylxanthogenate.

Examples of bi- or polycyclic amines which may be used are: 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU), 1,5-diazabicyclo [4.3.0] non-5-ene (DBN), 1,4-diazabicyclo [2.2.2] octane (DABCO), 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) and 7-methyl-1,5,7-triazabicyclo [4.4. 0] dec-5-ene.

As guanidine derivatives can be used, for example: diphenylguanidine (DPG), di-o-tolylguanidine (DOTG) and o-tolylbiguanide (OTBG).

Examples of dithiophosphates which can be used are: zinc dialkydithiophosphates (chain length of the alkyl radicals C ₂ to C ₁₆ ), copper dialkyldithiophosphates (chain length of the alkyl radicals C ₂ to C ₁₆ ) and dithiophosphoryl polysulfide.

For example, dithiobiscaprolactam can be used as caprolactam.

As thiourea derivatives, for example, N, N'-diphenylthiourea (DPTU), diethylthiourea (DETU) and ethylene thiourea (ETU) can be used.

Also suitable as additives are, for example: zinc diamine diisocyanate, hexamethylenetetramine, 1,3-bis (citraconimidomethyl) benzene and cyclic disulfanes.

In the case of hydroxyl-containing nitrile rubbers, it is possible to use a diisocyanate crosslinking as a further crosslinking method, it being possible for the diisocyanates used to be of monomeric or polymeric type and furthermore to contain at least two isocyanate groups. As diisocyanates, the following may be used singly or as a mixture, for example: toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, methylcyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1 , 3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1,5-naphthyl diisocyanate, xylylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,2-ethane diisocyanate, 1,3-propane diisocyanate, 1,4-butane diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,4-cyclohexanediisocyanate, 1,6-hexamethylene diisocyanate uretdione, 1,6-hexamethylene diisocyanate biuret, 1,6-hexamethylene diisocyanate isocyanurate and isophorone diisocyanate.

In the case of carboxyl-containing nitrile rubbers, a polyamine crosslinking method can be used as a further crosslinking method, the polyamines used containing at least 2 amino groups, or these are formed in-situ during the vulcanization. As polyamines, for example, aliphatic polyamines, such as hexamethylenediamine, hexamethylenediamine carbamate, hexamethylenediamine cinnamaldehyde adducts or hexamethylenediamine dibenzoatsalze or aromatic polyamines such as 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 4,4'-methylenedianiline, m Phenylenediamine, p-phenylenediamine or 4,4'-methylene-bis (o-chloroaniline). Reagents having at least 2 hydrazide units such as isophthalic dihydrazide, adipic dihydrazide or sebacic dihydrazide are also suitable.

The additives mentioned as well as the crosslinking agents can be used both individually and in mixtures. The following substances for crosslinking the nitrile rubbers are preferably used: sulfur, 2-mercaptobenzothiazole, tetramethylthiuram disulfide, tetramethylthiuram monosulfide, zinc dibenzyldithiocarbamate, dipentamethylenethiuram tetrasulfide, Zinkdialkydithiophosphat, dimorpholyl, tellurium diethyldithiocarbamate, nickel dibutyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dimethyldithiocarbamate and Dithiobiscaprolactam.

The crosslinking agents and additives mentioned above can each be used in amounts of about 0.05 to 15 5 phr, preferably 0.1 to 12 phr, in particular 0.5 to 10 phr.

In the case of the sulfur crosslinking according to the invention, it may also be sensible to use, in addition to the crosslinking agents and the additives mentioned above, further inorganic or organic substances, e.g. Zinc oxide, zinc carbonate, lead oxide, magnesium oxide, saturated or unsaturated organic fatty acids and their zinc salts, polyalcohols, aminoalcohols, e.g. Triethanolamine and amines, e.g. Dibutylamine, dicyclohexylamine, cyclohexylethylamine and polyetheramines.

In addition, scorch retarders can also be used. These include cyclohexylthiophthalimide (CTP), N, N'-dinitrosopentamethylenetetramine (DNPT), phthalic anhydride (PTA) and diphenylnitrosamine. Cyclohexylthiophthalimide (CTP) is preferred.

In addition to the addition of the crosslinker (s), the nitrile rubber of the invention may also be mixed with other customary rubber additives.

These include, for example, the typical and art-known substances such as fillers, filler activators, antiozonants, anti-aging agents, antioxidants, processing aids, extender oils, plasticizers, reinforcing materials, and mold release agents.

As fillers, for example, carbon black, silica, barium sulfate, titanium dioxide, zinc oxide, calcium oxide, calcium carbonate, magnesium oxide, alumina, iron oxide, aluminum hydroxide, magnesium hydroxide, aluminum silicates, diatomaceous earth, talc, kaolins, bentonites, carbon nanotubes, Teflon (the latter preferably in powder form), or Silicates are used.

Suitable filler activators are, in particular, organic silanes, for example vinyltrimethyloxysilane, vinyldimethoxymethylsilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, N-cyclohexyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, isooctyltrimethoxysilane, isooctyltriethoxysilane Hexadecyltrimethoxysilane or (octadecyl) methyldimethoxysilane into consideration. Further filler activators are, for example, surfactants such as triethanolamine and ethylene glycols having molecular weights of 74 to 10,000 g / mol. The amount of filler activators is usually 0 to 10 phr based on 100 phr of the nitrile rubber.

As anti-aging agents it is possible to add to the vulcanizable mixtures those already described in connection with the latex coagulation in this application. They are usually used in amounts of about 0 to 5 phr, preferably 0.5 to 3 phr, based on 100 phr of the nitrile rubber.

As mold release agents there are e.g. saturated or partially unsaturated fatty and oleic acids and their derivatives (fatty acid esters, fatty acid salts, fatty alcohols, fatty acid amides), furthermore products which can be applied to the mold surface, such as e.g. Products based on low molecular weight silicone compounds, products based on fluoropolymers and products based on phenolic resins.

The mold release agents are used as a blend component in amounts of about 0 to 10 phr, preferably 0.5 to 5 phr, based on 100 phr of the nitrile rubber.

Also, the gain with reinforcements (fibers) made of glass according to the teaching of US Patent No. 4,826,721 is possible as well as the reinforcement by cords, fabrics, fibers of aliphatic and aromatic polyamides (Nylon®, Aramid®), polyesters and natural fiber products.

The invention further provides a process for the preparation of vulcanizates based on at least one nitrile rubber, which may also be completely or partially hydrogenated, which comprises using the vulcanizable mixture of a crosslinking described above subjected, preferably by increasing the temperature or photochemical activation. This is particularly preferably carried out in the context of a shaping process, in particular using an injection molding process.

The invention likewise relates to the vulcanizate obtainable in the process, which is preferably a molded part and in particular produced in the aforementioned injection molding process.

By this method, a variety of moldings can be made, e.g. Seals, caps, hoses or membranes. In particular, the nitrile rubbers according to the invention, which may also be completely or partially hydrogenated, for the production of O-ring seals, flat gaskets, shaft seals, gaskets, sealing caps, dust caps, Steckerdichtungen, Thermoisolierschläuchen (with and without PVC additive), oil cooler hoses, Luftansaugschläuchen, power steering hoses or pump diaphragms

As an alternative to the direct production of moldings based on the nitrile rubber according to the invention, it is also possible that either (i) a metathesis reaction or (ii) a metathesis reaction and a subsequent hydrogenation or (iii) only one Hydrogenation connects. These metathesis or hydrogenation reactions are both well known to the skilled person and described in the literature.

For example, the metathesis is off WO-A-02/100941 as well as the WO-A-02/100905 known and can be used for molecular weight reduction.

Hydrogenation can be carried out using homogeneous or heterogeneous hydrogenation catalysts. It is also possible to carry out the hydrogenation in situ, i. in the same reaction vessel in which optionally before the metathesis degradation was carried out and without need to isolate the degraded nitrile rubber. The hydrogenation catalyst is simply added to the reaction vessel.

The catalysts used are usually based on rhodium, ruthenium or titanium, but it is also possible to use platinum, iridium, palladium, rhenium, ruthenium, osmium, cobalt or copper either as metal or preferably in the form of metal compounds (see, for example, US Pat US-A-3,700,637 . DE-A-25 39 132 . EP-A-0 134 023 . DE-OS 35 41 689 . DE-OS 35 40 918 . EP-A-0 298 386 . DE-OS 35 29 252 . DE-OS 34 33 392 . US-A-4,464,515 and US-A-4,503,196 ).

Suitable catalysts and solvents for homogeneous phase hydrogenation are described below and are also exhaustive DE-A-25 39 132 and the EP-A-0 471 250 known The selective hydrogenation can be achieved, for example, in the presence of a rhodium- or ruthenium-containing catalyst. It is possible, for example, to use a catalyst of the general formula

(R ¹ _m B) ₁ MX _n ,

wherein M is ruthenium or rhodium, R ^{1 are the} same or different and represent a C ₁ -C ₈ alkyl group, a C ₄ -C ₈ cycloalkyl group, a C ₆ -C ₁₅ aryl group or a C ₇ -C ₁₅ aralkyl group. B is phosphorus, arsenic, sulfur or a sulfoxide group S = O, X is hydrogen or an anion, preferably halogen and more preferably chlorine or bromine, 1 is 2,3 or 4, m is 2 or 3 and n is 1, 2 or 3, preferably 1 or 3. Preferred catalysts are tris (triphenylphosphine) rhodium (I) chloride, tris (triphenylphosphine) rhodium (III) chloride and tris (dimethyl sulfoxide) rhodium (III) chloride and tetrakis ( triphenylphosphine) rhodium hydride of the formula 1 [(C ₆ H ₅ ) ₃ P] ₄ RhH and the corresponding compounds in which the triphenylphosphine has been wholly or partly replaced by tricyclohexylphosphine. The catalyst can be used in small quantities. An amount in the range of 0.01-1% by weight, preferably in the range of 0.03-0.5% by weight, and more preferably in the range of 0.1-0.3% by weight based on the weight of the polymer is suitable.

It is usually useful to use the catalyst together with a co-catalyst which is a ligand of the formula R ¹ _m B, where R ¹ , m and B have the meanings given above for the catalyst. Preferably m is 3, B is phosphorus and the radicals R ¹ may be the same or different. Preference is given to co-catalysts with trialkyl, tricycloalkyl, triaryl, triaralkyl, diaryl-monoalkyl, diaryl-monocycloalkyl, dialkyl-monoaryl, dialkylmonocycloalkyl, dicycloalkyl-monoaryl or dicycloalkyl-monoaryl radicals.

Examples of co-catalysts can be found, for example, in US-A-4,631,315 , Preferred co-catalyst is triphenylphosphine. The co-catalyst is preferably used in amounts in a range of 0.3-5 wt.%, Preferably in the range of 0.5-4 wt.%, Based on the weight of the nitrile rubber to be hydrogenated. Furthermore, the weight ratio of the rhodium-containing catalyst to the cocatalyst is preferably in the range from 1: 3 to 1:55, particularly preferably in the range from 1: 5 to 1:45. Based on 100 parts by weight of the nitrile rubber to be hydrogenated, suitably 0.1 to 33 parts by weight of the co-catalyst, preferably 0.5 to 20 and most preferably 1 to 5 parts by weight, especially more than 2 but less than 5 parts by weight of co-catalyst based 100 parts by weight of the nitrile rubber to be hydrogenated.

The practical implementation of this hydrogenation is the expert from US-A-6,683,136 well known. It is usually carried out by subjecting the nitrile rubber to be hydrogenated in a solvent such as toluene or monochlorobenzene at a temperature in the range of 100 to 150 ° C and a pressure in the range of 50 to 150 bar for 2 to 10 hours with hydrogen.

Hydrogenated nitrile rubbers in the context of this invention are understood to mean wholly or partially hydrogenated nitrile rubbers and, corresponding to hydrogenation, a complete or partial reaction of the double bonds present in the starting nitrile rubber, preferably at least 50%, particularly preferably 70-100%, particularly preferably 80-100%. ,

When using heterogeneous catalysts are usually supported catalysts based on palladium, z. B. supported on carbon, silica, calcium carbonate or barium sulfate.

The optionally hydrogenated nitrile rubbers obtained after the metathesis and / or hydrogenation reaction of the nitrile rubbers according to the invention can be introduced into vulcanizable compositions analogously to the nitrile rubbers according to the invention and used for the preparation of vulcanizates and moldings based on such vulcanizates.

Examples I Preparation of nitrile rubbers A, B, C, D, E and F. Inventive Examples and Comparative Examples

The preparation of the nitrile rubbers AF used in the following examples series was carried out according to the recipes and polymerization conditions given in Table 1, all starting materials in parts by weight based on 100 parts by weight of the monomer mixture are given. <b><u> Table 1: </ u></b> nitrile rubber A B C D e F comparison comparison comparison butadiene 62 62 62 62 62 62 acrylonitrile 38 38 38 38 38 38 Total amount of water 200 200 200 200 200 200 Edenor ^® HTiCT ¹⁾ 2.20 2.20 2.20 2.20 2.20 2.20 t-DDM ²⁾ 0.30 0.30 0.50 0.50 0.75 0.75 Trigonox NT 50 ³⁾ 0.02 0.02 0.02 0.02 0.02 0.02 Premix FeSO ₄ ⁴⁾ 0,022 - 0.026 - 0,022 - Premix FeCl ₂ ⁴⁾ - 0,030 - 0.026 - 0,022 diethylhydroxylamine 0.4 0.4 0.4 0.4 0.4 0.4 Vulkanox BKF ^{® 5)} 0.3 0.3 0.3 0.3 0.3 0.3 pH ⁶⁾ 11.0 ± 1.0 11.0 ± 1.0 11.0 + 1.0 11.0 ± 1.0 11.0 ± 1.0 11.0 ± 1.0 Polymerization temperature [° C] 13.0 ± 0.5 13.0 ± 0.5 13.0 ± 0.5 13.0 ± 0.5 13.0 ± 0.5 13.0 ± 0.5 Polymerization conversion [%] 81.7 74.8 90.1 90.3 76.3 77.6 Polymerization time [h] 8.5 7 7 7 7 7.5 1) Edenor ^® HTiCT: selectively hardened tallow fatty acid (commercial product "Edenor HTiCT" Cognis GmbH)
2) t-DDM: (tertiary dodecylmercaptan); Lanxess Germany GmbH
3) p-menthane hydroperoxide (Trigonox NT 50 from Akzo-Degussa)
4) containing the reducing agent Rongalit C (sodium salt of a Sulfinsäurederivates) and the Fe (II) salt in the amounts indicated below.
5) 2 - [(2-hydroxy-5-methyl-3-tert-butylphenyl) methyl] -4-methyl-6-tert-butylphenol; Lanxess Germany GmbH
6) measured at the beginning of the polymerization

The preparation of the nitrile rubbers was carried out batchwise in a 5 l autoclave with stirrer. The autoclave batches each used 1.25 kg of the monomer mixture and a total amount of water of 2.1 kg and EDTA in an equimolar amount relative to the Fe-II. Of the amount of water, 1.9 kg were introduced with the emulsifier Edenor HtiCT and sodium hydroxide in an autoclave and rinsed with a stream of nitrogen. Thereafter, the destabilized monomers and the amount of the molecular weight regulator t-DDM indicated in Table 1 were added and the reactor was sealed. After the thermostatization of the reactor contents, the polymerizations were started by the addition of aqueous solutions of inventive or non-inventive iron (II) salts (in the form of premix solutions) and of para-menthane hydroperoxide (Trigonox NT50).

The premix solution contained 0.986 g of Fe (II) SO ₄ .7H ₂ O or 0.845 g of Fe (II) Cl ₂ .4H ₂ O and 2.0 g of Rongalit C on 400 g of water. Calculating the water of crystallization from the iron compounds, we obtain for both premix solutions each used amount of 0.539 g based on 400 g of water.

The course of the polymerization was followed by gravimetric conversion determinations. When the yields given in Table 1 were reached, the polymerization was stopped by addition of an aqueous solution of diethylhydroxylamine. Unreacted monomers and other volatiles were removed by steam distillation.

Before coagulation of the respective NBR latex of this respectively with a 50% dispersion of Vulkanox BKF ^® (0.3% Vulkanox BKF ^® wt. Based on NBR solid) was added. It was then coagulated, washed and dried the crumb obtained.

The dried NBR rubbers were determined by Mooney viscosity, MSR, ACN content, glass transition temperature, as well as their onset and offset point, and by the Gordon-Taylor relationship T _g = 1.4564 * [ ACN ] - 77.147 calculated therefrom difference value (ΔACN) of the ACN distribution (ΔACN = ACN (offset) - ACN (Onset)).

The resulting solid rubbers had the following properties (Table 2): <b><u> Table 2: </ u></b> nitrile rubber A B C D e F comparison comparison comparison ACN content (%) 36.2 36.4 35.5 35.3 36.1 36.6 Mooney Viscosity ML (1 + 4 @ 100 ° C) (MU) 134 142 80 76 30 25 MSR (Mu / s) 0.358 0,383 0,386 0.410 0.588 0.717 Glass transition temperature T _G (° C) -23.9 -23.7 -25.8 -24.5 -24.7 -23.1 Onset (° C) -30.9 -29.4 -33.0 -31.4 -31.2 -28.4 Offset (° C) -16.6 -17.4 -17.4 -17.1 -17.8 -17.3 ΔACN (wt%) 9.8 8.2 10.7 9.8 9.2 7.6

Table 3 clearly shows that with the process according to the invention, nitrile rubbers are obtained which clearly differ from those nitrile rubbers which were obtained by means of a redox system by using the special redox system. (II) sulfate differs. The new nitrile rubbers have a much more uniform monomer distribution, which is clearly evident from the lower ΔACN values in the polymers. The visibly higher MSR values of the nitrile rubbers of the invention also show that the nitrile rubbers according to the invention have a significantly lower long-chain branching.

II Preparation of nitrile rubber latex polymers G and H (Inventive Example and Comparative Example)

The preparation of the nitrile rubbers G and H used in the following examples was carried out according to the base formulation given in Table 3, all starting materials in parts by weight based on 100 parts by weight of the monomer mixture being indicated. Table 3 also lists the respective polymerization conditions. <b><u> Table 3: </ u></b> nitrile rubber G H butadiene 61.4 61.4 acrylonitrile 36 36 2-Hydroxethylmethaerylat 2.6 2.6 Total amount of water 220 220 Texapon ^® K-12 ¹⁾ 3.0 3.0 Na ₂ SO ₄ 0.12 0.12 t-DDM ²⁾ 0.54 0.54 Trigonox NT 50 ³⁾ 0.02 0.02 Premix FeSO ₄ ⁴⁾ 0,030 - Premix FeCl ₂ ⁴⁾ - 0,030 diethylhydroxylamine 0.2 0.2 Winstay 29 / Naugawhite ⁵⁾ 0.18 0.18 pH 7.0 ± 1.0 7.0 ± 1.0 Polymerization temperature [° C] 8.0 ± 0.5 8.0 ± 0.5 Polymerization conversion [%] 86.1 84.2 Polymerization time [h] 7.0 6.5 ¹⁾ Texapon.RTM ^® K-12: sodium lauryl sulfate (commercial product "Texapon.RTM K-12" from Cognis GmbH)
²⁾ t-DDM: (tertiary dodecylmercaptan); Lanxess Germany GmbH
³⁾ p-menthane hydroperoxide (Trigonox NT 50 from Akzo-Degussa)
⁴⁾ Composition as indicated in the table and at the top of the text
⁵⁾ Mixture of 25 g of Sorbilene Mix (mixture of sorbitan esters and ethoxylated sorbitan esters) from Lamberti, 38 g Naughawhite (2,2'-methylenebis (6-nonyl-p-cresol) from Chemtura), 125 g Wingstay 29 (styrenated Diphenylamine) from Eliokem and 63 g of water

The solid rubbers obtained had the properties given in Table 4, which were determined as indicated for Examples A to F. <b><u> Table 4: </ u></b> nitrile rubber G H ACN content (%) 32.2 35.0 Mooney Viscosity ML (1 + 4 @ 100 ° C) (Mu) 30 25 MSR (Mu / s) 0.578 0.633 Incorporation Termonomer (wt%) ¹ 1.4 1.7 Glass transition temperature T _G (° C) -34.5 / -22.0 -23.9 Onset (° C) -38.9 / -25.9 -29.4 Offset (° C) -29.1 / -17.5 -17.2 ΔACN (wt%) 12.5 ² 8.4 ¹⁾ Determined by ¹ H-NMR analysis
²⁾ As sum of the individual selectivities of ΔACN (1) + ΔACN (1) = ΣΔACN

Table 5 shows here that the nitrile terpolymers obtained with the specific Fe (II) chloride based redox system clearly have a more uniform monomer distribution (indicated by the lower ΔACN values in the polymers) and also a lower long chain branching (evidenced by the higher MSR Value). Two glass transition temperatures were measured for Comparative Example G: From this it can be concluded that the non-inventive use of Fe (II) (SO ₄ ) does not lead to a uniform copolymer, but rather polymers are formed which differ so greatly with respect to the monomer distribution that two Tg values were measured.

III Preparation of Vulcanizates of Nitrile Rubbers E and F (Inventive Example and Comparative Example)

The vulcanizates V1 and V2 were prepared from the nitrile rubbers E and F according to the method described below. The components of the mixtures are based on 100 parts of rubber and given in Table 5. <b><u> Table 5: </ u></b> mixture V1 V2 (comparison) Polymer F 100 Polymer E 100 Carbon black IRB 7 ¹⁾ 40 40 Edenor ^® C 18 98-100 ²⁾ 1 1 SULFUR SPIDER ³⁾ 1.54 1.54 VULKACIT ^® NZ / EGC ⁴⁾ 0.7 0.7 IRM 91 ⁵⁾ 3 3 Total phr 146.24 146.24 density g / cm ³ 1.168 1.168 ¹⁾ IRB 7: carbon black (Sid Richardson Carbon Co.)
²⁾ Edenor ^® C 18 98-100: Stearic acid (Caldic)
³⁾ SULFUR SPIDER: sulfur (S ₈ ) (Krahn Chemie GmbH)
^{4) ®} Vulkacit NZ / EGC: N-tert-butyl-2-benzothiazole sulfenamide (TBBS) (Lanxess GmbH Germany)
⁵⁾ IRM 91: Zinc (II) oxide: (Midwest Zinc)

The blends were made in a Banbury mixer. For this purpose, the rubber and all the additives listed in Table 5 were mixed for a total of 4 minutes at a maximum temperature of up to 120 ° C. For this purpose, the rubber was introduced into the mixer, after 1 minute all further additives were added and after 2 more minutes a sweeping step was carried out. After a total of 4 minutes, the rubber was ejected from the mixer. The resulting vulcanizates had the properties given in Table 6.

The cure history of the MDR and its analytical data were measured on a Monsanto rheometer MDR 2000 according to ASTM D5289-95. <b><u> Table 6: </ u></b> mixture V1 V2 (comparison) MDR (130 ° C / 60min) Max. Torque (dNm) 19.06 20.43 t ₁₀ (min) 14.70 14,30 t ₉₅ (min) 44,10 41.83 MDR (170 ° C / 30min) Max. Torque (dNm) 17.85 19.22 t ₁₀ (min) 1.29 1.31 t ₉₅ (min) 5.87 4.91

Corresponding to the lower branching of the polymer F, the maximum torque compared with the vulcanizate of the comparative polymer E is slightly lower, but also at a very good level.

The novel polymer F is distinguished by significantly improved flow properties, which represent an important processing parameter. This can be shown by appropriate Rheovulkameter measurements. The Rheovulkameter is generally used to test the processing behavior of rubber compounds (injection molding).

A precisely weighed mixture sample with the compositions given in Table 5 for V1 or V2 was placed in a storage room and introduced by means of a piston through a nozzle into injected a heated test form. Table 7 shows the parameters and the results of Rheovulkameter measurement: <b><u> Table 7: </ u></b> mixture V1 V2 Rheovulkameter Preheating temperature (° C) 100 Preheating time (sec) 100 Injection pressure (bar) 97 Bulb temperature (° C) 100 Nozzle temperature (° C) 100 Injection time (sec) 20 Vulcanization time (min) 5 Vulcanization temperature (° C) 180 Spray volume (cm ³ ) 2.02 1.85 Injection speed (cm ³ / sec) 0,099 0.091 Filling degree (%) 65.5 59.4

Claims (15)

1. Process for producing nitrile rubbers by emulsion polymerization of at least one α,β-unsaturated nitrile, at least one conjugated diene and optionally one or more other copolymerizable monomers, characterized in that the emulsion polymerization is carried out using a redox system which comprises

   (i) as oxidizing agent at least one peroxo compound,

   (ii) at least one reducing agent and

   (iii) Fe(II) chloride.
2. Process according to Claim 1, wherein use is made as oxidizing agent (i) of hydrogen peroxide, peroxodisulphates, peroxodiphosphates, hydroperoxides, peracids, peracid esters, peracid anhydrides or peroxides having two organic radicals.
3. Process according to Claim 1, wherein use is made as oxidizing agent (i) of sodium, potassium or ammonium salts of peroxodisulphuric acid or peroxodiphosphoric acid, t-butyl hydroperoxide, cumene hydroperoxide, pinane hydroperoxide, p-menthane hydroperoxide, dibenzoyl peroxide, 2,4,-dichlorobenzoyl peroxide, di-t-butyl peroxide, dicumyl peroxide, t-butyl perbenzoate or t-butyl peracetate.
4. Process according to any of Claims 1 to 3, wherein use is made as reducing agent (ii) of sodium formaldehyde-sulphoxylate, sodium benzaldehyde-sulphoxylate, reducing sugars, ascorbic acid, sulphenates, sulphinates, sulphoxylates, dithionite, sulphite, metabisulphite, disulphite, sugars, urea, thiourea, xanthogenates, thioxanthogenates, hydrazinium salts, amines and amine derivatives, preferably aniline, dimethylaniline, monoethanolamine, diethanolamine or triethanolamine.
5. Process according to any of Claims 1 to 4, wherein the emulsion polymerization is carried out in the presence of sodium ethylenediaminetetraacetate (EDTA), sodium silicate, sodium pyrophosphate or sodium polyphosphate or trisodium phosphate.
6. Process according to any of Claims 1 to 5, wherein use is made as oxidizing agent (i) of pinane hydroperoxide or p-menthane hydroperoxide, as reducing agent (ii) of sodium formaldehyde-sulphoxylate and Fe(II) chloride in the form of FeCl₂*4 H₂O, and additionally EDTA is used in the emulsion polymerization.
7. Process according to any of Claims 1 to 6, wherein the emulsion polymerization is followed by either (i) a metathesis reaction for molecular weight reduction or (ii) a metathesis reaction for molecular weight reduction and a subsequent hydrogenation or (iii) only a hydrogenation.
8. Nitrile rubbers having repeating units derived from at least one α,β-unsaturated nitrile, at least one conjugated diene and optionally one or more other copolymerizable monomers, obtainable by emulsion polymerization of at least one α,β-unsaturated nitrile, at least one conjugated diene and optionally one or more other copolymerizable monomers using a redox system comprising

   (i) as oxidizing agent at least one peroxo compound,

   (ii) at least one reducing agent and

   (iii) Fe(II) chloride.
9. Nitrile rubbers obtainable from the nitrile rubbers according to Claim 8 by subjecting them additionally to a metathesis reaction.
10. Hydrogenated nitrile rubbers obtainable from the nitrile rubbers according to Claim 8 by subjecting them to a hydrogenation reaction.
11. Hydrogenated nitrile rubbers obtainable from the nitrile rubbers according to Claim 8 by subjecting them to a metathesis reaction and a subsequent hydrogenation.
12. Vulcanizable mixtures comprising the nitrile rubber according to Claim 8 or 9 or the hydrogenated nitrile rubber according to Claim 10 or 11 and at least one crosslinker.
13. Vulcanizable mixtures according to Claim 12, further comprising at least one filler.
14. Process for producing vulcanizates, characterized in that the vulcanizable mixture according to Claim 12 is subjected to crosslinking, preferably by raising of the temperature or by photochemical activation.
15. Vulcanizates obtainable by the process according to Claim 14.